Electric valve



Sept. 91, 1930. l H COHN 1,775,588

ELECTRIC VALVE Filed 0913. 27, 1923 5 num/H601,

my, 411.@ m1-2mm lso Patented Sept. 9, 1930 UNITED sTATEs PATENT OFFICE HENNY COHN, 0F CHARLOTTENBURG. NEAR BEELIN, GERMANY, ASSIGNOR T0 THE FIRM DR. ERICH F. HUTH GES. M. B. H., 0F BERLIN, GERMANY nLEcraI-c VALVE Application illed October 27, 1923, Serial No. 671,161, and in Germany October 30, 1922.

This invention relates to electric valves that may be used as current rectifiers, ampli fiers, detectors or the like.

As well known, such tubes or valves operate with a hot cathode consisting of a metallic lament e. g. of tungsten or the like, or ot a suitable core entirely or partially covered with an oxid layer. These cathodes are usually heated by means of a heating battery which is continuously connected in circuit during the operation of the device. For this reason such heating batteries must be of fairly large size and, because of this and the necessity'oi" looking after their charging, etc., they are inconvenient.

ln accordance with the present invention,`

means are provided whereby the necessity of providing such heating battery is eliminated. This is accomplished in such a manner that during the operation of the valve the cathode is heated by the current which flows therefrom towards an anode whereby the capacity of the cathode to emit electrons is maintained. t is not necessary to connect the heating battery into the cathode circuit during the actual operation of the tube. Such battery or any other heat source is connected in circuitfor a very short *time`r possibly only for a fraction of a second for the purpose of causing the cathode to glow and is then again disconnected from the circuit upon the starting of the anode current or emission of electrons. As a result of this a very small heating battery may be provided. It the hot cathode is fed from a power line or a current source which serves also for any other purpose (e. g. the anode current source) then. in determining the point at which this source should be tapped only these short circuit closures need be taken'into consideration.

As above stated such self heating of the cathode by means ofthe electron emission current may be practised with filament or plate cathodes of tungsten, Wolfram or other materials. However, the arrangement is particularly applicable if an oxid layer of earth alkalies or of other suitable compositions and constructions are used. This oxid layer has the property of o'ering a higher resistance to the passage of the current than is the case with naked electrical conductors. The electrons i. e. the anode current traversing this covering must therefore overcome a higher resistance and the resulting Joule effect will cause the heating of the cathode in the re-` quired manner.

The use of a covering layer which as com pared with the usual metallic conductors increases the resistance to the emission of electrons, has also a further advantage. As well n known. when the load is increased and the valve is more eiliciently operated. the anode will also be caused to glow by the electrons and will become therefore a source of elec tronic emission. If only the cathode and not the anode is provided with a covering layer which aids in-the emission of electrons then. even in case both the anode and the cathode are caused to glow, the quantity of the electrons emitted by the hot cathode will be exwhich the cathode is covered with mixturesof combinations of earth alkali metals, in-

clusive or exclusive-of oxids, hydroxids andsalts of nitrogen containing acids, which are applied as a jelly on a carrier or are powdered and then molded into forms and heated.

The invention is not limited to subjecting the anode to the eifect of heat. The eiifect of light on the anode may also be utilized in which case the cathode is covered with a layer which under the action of light rays will emit electrons (electric photocell). By using valves provided with such crt-hodes` during the operation of the device after the stream of electrons has been startcdl the glowing anode itself may be used as a source of light.

The invention will be described more in detail by means of thc drawings in which Figs. 1-4 schematically illustrate various Si l )till l vided between the cathode 2 and the anode 5 which may be connected in circuit directly or through the agency'of a transformer. lt is desired to rectify the alternating current supplied from lthis source. As soon as the switch 4 is moved into position I the cathode is brought to a glow and the condition is reached in which it will be maintained glowing due to the electronic emission. Then the switch 4 is moved into position II disconnecting the heating battery. If desired, the switch may be moved into position III in which the cathode is bi-polarly connected to the alternating current source and therefore into the anode circuit.

As shown in Fig. 2 the same circuit arrangement may be used also with a multiple cathode` more particularly with a cathode divided and into two sections 2 and 2. The sections of the cathode connected in parallel may be unipolarly connected at 7 with the heating battery 3 whereas the other poles 8 and 9 are separately connected with switches 4 and 4 andmay be connected through these switches with the battery 3 or separately through the conductors indicated in dotted lines with the anode circuit.

Obviously, as shown in Fig. 3 the sections 2 and 2 of the cathode may be permanently connected in parallel and then connected with the heating battery through a single switch 4 or disconnected from this battery and connected to the anode circuit.

In the circuit arrangement shown in F 2 a separate heating source may be provided for each section of the cathode. This is indicated in dotted lines at 3. Of course in this case the connection 10 vis left out.

Fig. 4 shows an arrangement in which the use of a heating current source is entirely avoided. The cathode 2 is heated from an alternating current source 6 which in the present case is a transformer provided with a tap 11 with which the cathodemay be connected by means of the switch 4 at the beginning of an o eration and disconnected after a few secon s or a fraction of asecond when the electronic emission begins. Obvi-` ously, this arrangement can be used also with 'other alternating current sources than a HENNY ooHN. 

